CCD-based observations of PG 0856+121 and a theoretical analysis of its oscillation modes ^*

¹ Universidade de Vigo, Departamento de Física Aplicada, Área de Física da Terra, Astronomía e Astrofísica, Facultade de Ciencias, Campus Lagoas-Marcosende, 36200 Vigo, Spain
² Instituto de Astrofísica de Canarias, c/ Vía Láctea s/n, 38200 La Laguna, Tenerife, Spain
³ CALTECH, MS 150-21, Pasadena, CA 91125, USA
⁴ Departamento de Astrofísica, Universidad de La Laguna, Tenerife, Spain
⁵ Department of Physics and Astronomy, University of Delaware, Newark, DE 19716, USA

Corresponding author: A. Ulla, ulla@uvigo.es

Received: 5 July 2000
Accepted: 29 January 2001

Abstract

BVRI CCD-based and near-IR (J) imaging, together with unfiltered photometry of the hot subdwarf B star PG 0856+121, are reported. Two close, faint, red, point-like sources are resolved. They account for the previously reported IR excess observed in this hot subdwarf. In addition, the new unfiltered differential photometry of PG 0856+121 confirms its previously reported pulsational nature. A comparison with the oscillation modes of stellar models suggests the presence of g modes.